A computer typically contains an internal clock (e.g., a master clock) that regulates the rate at which instructions are executed and synchronizes all the various components of the computer. The rate at which instructions are executed is commonly referred to as a clock speed or clock rate. The clock rate is typically determined by the frequency of a master clock signal of a master clock, such as an oscillator crystal. For example, the master clock may produce a fixed sine wave. Electronic circuitry translates the master clock signal into a square wave at the same frequency and transmits the clock signal to the components of the computer, such as processors, memories, and so on.
Clock rates for the computer components are determined at the end of the manufacturing process through testing of the computer components. However, the clock rate of a component can be adjusted. For example, a processor can be overclocked by running the processor at a higher clock rate than specified by the manufacturer. Overclocking the processor causes the processor to run faster thereby increasing the power of the processor. Underclocking, also known as downclocking, is the practice of adjusting a component to run at a lower clock rate than specified by the manufacturer. Underclocking is commonly used to reduce the power consumption of a processor, increase battery life, reduce heat emission, and the like.